In the past 30 days I've been working with the amp across a range of speakers and with many different output tubes. (Maybe I just work too much, but I could swear I wrote this once before, yet I can't seem to find it!) So at the risk of repeating myself...

I've been playing with different output tubes, bias levels, and output transformer ratios. I've been wrestling with trying to decide what output transformer design I should use, ie. primary impedances and ultra-linear or not. I feel like I'm making good progress on this front, which was my biggest concern.

I've also learned more about having twice the capacitance of the TORII MONO's combined with lower voltages. This part of the power supply is like the camshaft in a stroked out high cubic inch motor. Getting the lift and duration and overlap right takes a lot of trial and error unless you're into computer simulations, which I am really not. The speaker would be the rear end gear against the weight of the car. In a nutshell, we're talking about the speed of the power supply at given frequencies and combinations of frequencies. The caps were so huge that below 120 Hz when used on the wrong output tap (which will happen in real life) and on worse case speakers, the bass lacked attack and control, although it was incredibly powerful and deeper than I've ever heard it. I found bypassing it with equal quality electrolytic by F&T fixed the low bass problem but getting the values right is like designing a crossover. It took two paralleled caps to fix both the low bass and mid bass. I'm now happy with it.

So far my favorite tubes have been the KT66 followed by the KT120's as a close second that I anticipate will actually be determined by the speakers and subjective tastes, so next time I write, I may like the 120's better than the 66's. That's how this hobby goes! Point being you can easily use either, or KT88, 6550, EL34, 6CA7.

I also have given up on the negative feedback. The amp doesn't need it, so it's been wearing a white wedding dress for the past two weeks and never sounded better.

I took an opportunity last night to listen to it on non-decware speakers which the amplifier is largely targeted to... i.e. $7500.00 and up loudspeakers that are the typical 86 / 87dB sensitivity. To that effect Dave Janszen came over with his latest electrostatic hybrids and we compared the TORII MONO's to the Mystery Amp until 1:30 A.M. and both liked the Mystery Amp a bit more. It was sweeter, a bit more organic and smoother. We started with the TORII MKIII but it didn't match well and had some detectible distortion in the low frequencies when turned up. The Monos made the speakers sing so we used them for most of the evening. The Mystery amp was tried in the final hours to see what would happen and we could detect no difference in power despite it being probably close to half that of the monos.

The Janszen speakers with the Mystery Amp turned out to be a digit killing combination. In other words, all 6 digit audio systems should be nervous at risk of being embarrassed.

If you're unfamiliar with JansZen speakers, these are around $7500 and have my full endorsement.

Very exciting that you are satisfied with the Mystery Amp at this point, and that it performs so well with less efficient speakers! I look forward to more impressions as you play the amp more. Or could it by chance be complete?!?!?

I am going to start experimenting with the output transformer ratios, wire gauge, core size and see what happens. Right now, the amp is nearly perfect on all my speakers when on the 4 ohm tap, regardless of the speakers actual impedance. I want to get it to sound like it does now or better on a higher tap with the same speakers. That would at minimum give me more voicing possibilities with a given speaker and ensure tight bass without feedback at all times.

That's the update. Still centering the sound and performance around the KT66.

Transformers have the biggest effect on a tube amplifier's sound in my world, so it came as no surprise that this latest intrusion into the amplifiers voicing would be big. (No that's not true... it came as a big surprise!) And now having just witnesses how different transformers effect the sound again, I still can't help but be amazed at just how much things can change!

After several evenings discussing the output winding topologies we recently tested some classic secondary arrangements with the typical taps against some dual secondary arrangements where windings of different lengths are combined on the same bobbin. The differences ranged from something that sounded typically real good, to something that sounded magical. Some interesting stuff since the only main difference is in the pattern of core saturation. I expected to have to strain to hear the difference, but instead I had to check and see if we were still listening to the same amplifier.

With this rather pleasant discovery I now know this amp is going to be hugely successful. Optimized for (but not limited to) KT66 output tubes, I'm currently witnessing it sound better than both the Zen Mono's and the TORII MK III. That doesn't mean it is, because it's still to new and there is some infatuation that will need to wear off before I can actually hear it objectively.

I'll keep you posted as I put the fine polish on it and continue to wrap my head around it. Right now my comment about the sound would be this: Generally liquidity and honesty are rarely found in the same amplifier, but this seems to be a reference for both. Almost too good to be true.

Steve, I hope you see this question and can clarify a point you made when listening to the Janszen speakers. We talked just yesterday about my plans to use the Torii MK3 with David's excellent speakers. When you said above in this thread that the Torii MK3 didn't match well I need to know if you meant in general or when compared to the mystery amp and the mono blocks?

When I got on the list for the Torii MK3 the only other high wattage option was the mono blocks which are not in my spending wheel house. From listening to the Torii with my speakers I know it won't drive the Janszens to the upper listening levels but I'm not sure I need that. If you meant that the amp didn't match well because of sonic issues then I am not sure what to do. It sure sounded like heaven to me. I may still need to learn more about the mystery amp. Is it really the amp I should be considering? I'm probably targeting into September on the waiting list as it is with the Torii MK3.

Please give me an honest assessment if I need to rethink using the Torii MK3 with the Janszen speakers. This will be my last amp and I'd rather not make a mistake. The Janszen speakers aren't going anywhere. They are keepers. Others with average efficiency speakers may also be interested in your take.

Okay, I know I should not ask...but my curiosity is getting the best of me.

KT66 run in Triode as well as ultra linear Pentode (switch on the fly)?I have no problem with turning the Amp off to switch between the two-if need be.

XLR (balanced inputs) as well as RCA line level (we got that peek-aboo?)

What is the input driver (preamp) tube? ....it does not look like a 6H30...but, more of a conventional one.... .

Listening to my SE84CS right now sitting in the next room typing this....Larry Carlton Playing sweetly.

So, why the Mystery Amp? I want low end + a little more headroom without adding a Sub. However, maintaining the Transparency & Timbre Texture of the SE84CS & CKC...or coming damn close.

Candidates Are:

Mystery Amp, Audio Research Reference 75 & BAT VK-55 SEI will run the AR or BAT direct via NAD M51 Dac, with its Balanced outputs to inputs of the Amp(s) or RCA to XLR adaptors run directly from my Audio Alchemy 3.0 Dac via remote as well.

Hope everyone is having a great summer. Cheers, Stone of Tone

PS-the SE84CS & CKC will always remain in use...because they will always do what no other Amps can do.........I just want another flavor as layed out in Steve's Car analogy. Steve's Monte Carlo is sweet-the paint and clear coat on it, are 2nd to none (plus under the hood).

Steve, I hope you see this question and can clarify a point you made when listening to the Janszen speakers. We talked just yesterday about my plans to use the Torii MK3 with David's excellent speakers. When you said above in this thread that the Torii MK3 didn't match well I need to know if you meant in general or when compared to the mystery amp and the mono blocks?

When I got on the list for the Torii MK3 the only other high wattage option was the mono blocks which are not in my spending wheel house. From listening to the Torii with my speakers I know it won't drive the Janszens to the upper listening levels but I'm not sure I need that. If you meant that the amp didn't match well because of sonic issues then I am not sure what to do. It sure sounded like heaven to me. I may still need to learn more about the mystery amp. Is it really the amp I should be considering? I'm probably targeting into September on the waiting list as it is with the Torii MK3.

Please give me an honest assessment if I need to rethink using the Torii MK3 with the Janszen speakers. This will be my last amp and I'd rather not make a mistake. The Janszen speakers aren't going anywhere. They are keepers. Others with average efficiency speakers may also be interested in your take.

Scott Marsh

Hi Scott,

The sound of the Torii MKIII on the Janszen speakers is wonderful. The catch is that you are limited to a modest volume during playback. When Dave was here testing the combo, he said he heard distortion in the lower frequencies. Rather than try different taps or adjust the bass dampening control on the MK III, we just put in a bigger amp because it was clear he wanted the ability to play the speakers loud on demand.

The Mystery Amp had no issues. It will be available by October, so my advise would be to either get it, or try the TORII MKIII and see for yourself if it is enough power for you. I know of one other customer who has these speakers and amp combo who loves it and has never complained of lack of power, so really only you can tell this for yourself.

Should the MKIII not be enough power, I would let you keep it until your Mystery Amp is ready to ship.

Okay, I know I should not ask...but my curiosity is getting the best of me.

KT66 run in Triode as well as ultra linear Pentode (switch on the fly)?I have no problem with turning the Amp off to switch between the two-if need be.

The fundamental characteristics of an amplifier's sound are different enough between Pentode and Triode that a great sounding amplifier would have to be voiced differently for each. I would rather pick the best sounding one, voice the amp to maximize that, so that's what I'm doing.

Quote:

XLR (balanced inputs) as well as RCA line level (we got that peek-aboo?)

Yes, RCA line level standard, fully transformer balanced XLR will be an option.

Quote:

What is the input driver (preamp) tube? ....it does not look like a 6H30...but, more of a conventional one.... .

6922, 6N1P, 6N23P

Listening to my SE84CS right now sitting in the next room typing this....Larry Carlton Playing sweetly.

So, why the Mystery Amp? I want low end + a little more headroom without adding a Sub. However, maintaining the Transparency & Timbre Texture of the SE84CS & CKC...or coming damn close.

Candidates Are:

Mystery Amp, Audio Research Reference 75 & BAT VK-55 SEI will run the AR or BAT direct via NAD M51 Dac, with its Balanced outputs to inputs of the Amp(s) or RCA to XLR adaptors run directly from my Audio Alchemy 3.0 Dac via remote as well.

Hope everyone is having a great summer. Cheers, Stone of Tone

PS-the SE84CS & CKC will always remain in use...because they will always do what no other Amps can do.........I just want another flavor as layed out in Steve's Car analogy. Steve's Monte Carlo is sweet-the paint and clear coat on it, are 2nd to none (plus under the hood).